When installing window frames in building structures it is necessary to bend, cut, and otherwise shape rigid metal framing elements. Many pieces have to be formed and shipped to the customer. The typical window installation also requires numerous fasteners such as nails, screws, and so forth, which add to production costs and installation time. It would be advantageous to have a flexible unitary clamping device capable of securing a window frame assembly by hand in the opening of a building structure firmly so that external seals compress against the building without the use of fasteners. Such a device would also be able to be preassembled to the frame so that fewer pieces would need to be shipped to the customer.